A genetic and cytogenetic map for the duck (Anas platyrhynchos)

A genetic linkage map for the duck (Anas platyrhynchos) was developed within a cross between two extreme Peking duck lines by linkage analysis of 155 polymorphic microsatellite markers, including 84 novel markers reported in this study. A total of 115 microsatellite markers were placed into 19 linkage groups. The sex-averaged map spans 1353.3 cM, with an average interval distance of 15.04 cM. The male map covers 1415 cM, whereas the female map covers only 1387.6 cM. All of the flanking sequences of the 155 polymorphic loci--44 monomorphic loci and a further 41 reported microsatellite loci for duck--were blasted against the chicken genomic sequence, and corresponding orthologs were found for 49. To integrate the genetic and cytogenetic map of the duck genome, 28 BAC clones were screened from a chicken BAC library using the specific PCR primers and localized to duck chromosomes by FISH, respectively. Of 28 BAC clones, 24 were detected definitely on duck chromosomes. Thus, 11 of 19 linkage groups were localized to 10 duck chromosomes. This genetic and cytogenetic map will be helpful for the mapping QTL in duck for breeding applications and for conducting genomic comparisons between chicken and duck.     

Precipitating antibodies of the duck (Anas platyrhynchos)

1. Ducks do not usually produce precipitating antibodies. However, when hyperimmunized with the dinitrophenyl (DNP)-human IgG (HIgG) conjugate, ducks made precipitating antibodies to the HIgG carrier, though not to the DNP hapten. 2. Precipitation did not require NaCl and occurred over a wide range of molarities and pH. 3. Antigenic and polyacrylamide gel analysis of affinity-purified antibodies, indicated that the major constituent of the antibody population was electrophoretically homogeneous 5.7S IgG. 4. The Ig heavy chains were in two populations, viz MW 37,000 and 41,000; non-precipitating duck 5.7S IgG antibodies to HIgG had only the MW 37,000 heavy chains. 5. It is suggested that duck precipitins belong to a previously unrecognized subclass of duck 5.7S IgG, with minor physical and antigenic differences from their non-precipitating counterparts.     

Retinohypothalamic pathway in the duck (Anas platyrhynchos)

Summary Retinohypothalamic connections were studied in the duck after unilateral optic nerve transection using both light and electron microscopic techniques. Degenerated endings of optic fibers were found only in a circumscribed part of the anterior hypothalamic area, i.e. the ventral region of the contralateral suprachiasmatic nucleus. Images of degenerating boutons were observed in frozen sections (method according to Johnstone-Bowsher), and their presence confirmed by electron microscopic examination. These degenerating boutons make synaptic contacts with dendrites or dendritic spines of neurons of the suprachiasmatic nucleus.In the same material, the decussation of the optic chiasma was studied with the light microscope. Uncrossed retinal fibers were found in the marginal optic tract, the basal optic root and occasionally also in the isthmo-optic tract.Dedicated to Professor Dr. W. Bargmann on the occasion of his 70th birthdaySupported by the DGRST and European Training Program Brain and Behaviour ResearchI wish to express my gratitude to Professor Andreas Oksche, who repeatedly offered me the scientific facilities at the Department of Anatomy of the University of Giessen, and who provided me with valuable neuroanatomical suggestions throughout the progress of these studies.     

Description of the mallard duck (Anas platyrhynchos) karyotype

The karyotype of the mallard duck, Anas platyrhynchos, was characterised on the basis of R and C bands. Chromosomal preparations obtained from in vitro blood lymphocyte cultures were RBG- and CBG-stained. The structures of nine and 14 pairs of chromosomes were analysed by the RBG and CBG chromosome banding techniques, respectively. The location of R bands, as well as the size and arrangement of constitutive heterochromatin blocks were determined. Ideograms of R and C banded patterns of the analysed chromosomes were drawn. The morphological makeup of the analysed chromosomes was assessed.     

Isolation,culture and differentiation of duck (Anas platyrhynchos) preadipocytes

In the present study, we isolated preadipocytes from the adipose tissue of Peking duck and subsequently cultured them in vitro. Cell counting kit-8 assay was employed to establish the growth curve of duck primary preadipocytes. Meanwhile, after the cells reaching full confluency, they were induced to differentiate into mature adipocytes by the addition of a cocktail containing dexamethasone, insulin, 3-isobutyl-1-methylxanthine, and oleic acid for 8 days. Successful differentiation was demonstrated by the development of lipid droplets and the expression of key marker genes including peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer binding protein-α (CEBP/α) and adipocyte fatty acid-binding protein (FABP4). Our results showed that duck primary preadipocytes began to adhere 12 h after seeding as short spindle shapes or litter triangles, which grew quickly 3 days post attachment and maintained stable after day 7. After 8 days the preadipocytes were induced to differentiate into mature adipocytes, which were stained red by oil red O. Additionally, it showed that during preadipocyte differentiation PPARγ mRNA was highly expressed at day 3, while CEBP/α and FABP4 mRNA peaked at day 5 and 8, respectively. These results indicate that we have successfully isolated and cultured Peking duck preadipocytes and successfully induced them to differentiate into mature adipocytes. This work could lay a foundation for further research into waterfowl adipogenesis.     

Corticoid uptake by the paraventricular nucleus in the hypothalamus of the duck,Anas platyrhynchos

3H-corticoids were localized by autoradiography in small neurons in the area of the magnocellular paraventricular nucleus of mallard ducks. Correlative data show that: (1) the label is principally unmetabolized steroid, (2) the hypothalamus competitively binds corticosterone, (3) the paraventricular nucleus contains immunoreactive neurophysin, is richly innervated by boutons of monoaminergic nerves and is involved in the adaptive response to osmotic stress.     

Ependymal and neuronal specializations in the lateral ventricle of the Pekin duck,Anas platyrhynchos

Summary The lateral ventricles of the Pekin duck, Anas platyrhynchos, display characteristic ependymal and hypendymal specializations. Adjacent to the nucleus accumbens and the basal pole of the lateral septum the ventricular surface shows a highly folded pattern either with protrusions into the ventricular lumen or deep invaginations into the brain tissue. These medial and basal ependymal folds are found exclusively in a circumscribed region extending over a range of 600 m in the rostrocaudal direction. Ependymal folds occurring in the lateral wall of the ventricles were traced up to the level of the interventricular foramen. Numerous capillaries are observed in the subependymal layer of these folds.By means of immunocytochemistry with antibodies against chicken vasoactive intestinal polypeptide (VIP) an aggregation of classical cerebrospinal fluid-contacting neurons is shown in the region of the nucleus accumbens and the lateral septum. These neurons are closely related to the ependymal folds. Additional VIP-immunoreactive neurons are scattered in deeper layers of the lateral septum and the nucleus accumbens. The latter are richly innervated by VIP-immunoreactive nerve fibers.The results of the present study are discussed with particular reference to the hypothesis of Kuenzel and van Tienhoven (1982) that ependymal specializations demonstrated in the lateral ventricles of the domestic fowl might represent a new circumventricular organ (lateral septal organ).The authors are greatly indebted to Professor A. Oksche for stimulating discussionsSupported by the Deutsche Forschungsgemeinschaft (Ko 758/2-2; 2-3) and the P. Carl Petersen Foundation     

Low genetic differentiation and close evolutionary connection between Anas platyrhynchos and Anas poecilorhyncha: data from RAPD-PCR analysis

Using RAPD-PCR, we examined genetic diversity and phylogenetic relationships in two groups of river ducks: Anas platyrhynchos, A. poecilorhyncha, A. strepera and A. crecca, A. formosa, A. querquedula. Molecular taxon-specific markers were found for teals (A. crecca, A. formosa, A. querquedula) and gadwall (A. strepera). Each of the species examined was shown to exhibit high genetic diversity. The mean levels of intraspecific genetic polymorphism in the groups of mallards (P = 77%) and teals (P = 74.5%) were approximately equal whereas the mean interspecific genetic distances in teals were significantly higher than in mallards (D = 0.432 and D = 0.336, respectively). The levels of interspecific genetic differentiation in the species groups were also different. The genetic distances between the teal species and between gadwall and mallards were equal to 0.668-0.971 while the genetic distance between mallard A. platyrhynchos and spot-billed duck A. poecilorhyncha was 0.401, which slightly exceeds the intraspecific values for mallards (0.356-0.377). The RAPD patterns for this species pair showed high variability and a lack of fixed differences. This was adequately reflected on both intra- and interspecific differences and on phylogenetic constructions in which the morphological species did not form their own clusters but were intermixed. In contrast to mallards, the other species, which showed high genetic variability, were reliably separated in phenogenetic and phylogenetic reconstructions. The possible explanations of the low genetic differentiation of A. platyrhynchos and A. poecilorhyncha are discussed.     

Neural mechanisms affecting pressor responses to angiotensins in the Pekin duck, Anas platyrhynchos

1. Administration of SQ20881 diminished pressor responses to intravenous (i.v.) injections of angiotensin I (AI), but not those to injections of angiotensin II (AII), in Pekin ducks, indicating the occurrence of a mechanism similar to the mammalian angiotensin-converting enzyme reaction. 2. Pressor responses to AII were enhanced by general anaesthesia with phenobarbital, pentobarbital, or a combination of both phenobarbital and pentobarbital. 3. Ganglionic blockade with mecamylamine enhanced the pressor responses to AII and NE, but not those to tyramine, in anaesthetized ducks. 4. It is proposed that the potentiating effects of general anaesthesia and ganglionic blockade on pressor responses were due both to a lowering of baseline blood pressure (BP) and an inhibition of the neural reflexes which normally buffer BP. Furthermore, it is suggested that the augmented responsiveness of anaesthetized, ganglion-blocked ducks shows that the pressor effect of AII is predominantly of peripheral, rather than central nervous system (CNS), origin.     

Annular bands of lymphoid tissue in the intestine of the mallard duck Anas platyrhynchos

The annular bands were studied by light and scanning electron microscopy in normal and hormonally bursectomized ducks (Anas platyrhynchos). The four annular bands are normal lymphoid structures of 5–10 mm wide and encircle the intestine at regularly spaced position, two on each side of Meckel's diverticulum. The anterior three are well defined, complete rings whereas the posterior-most encompasses about one half of the gut circumference. The bands are characterized by prominent follicles in the tunica muscularis, submucosa, and lamina propria. In addition, large numbers of diffusely organized lymphocytes fill the lamina propria and villus cores. Each nodule possesses germinal centre activity, as revealed by the characteristic macrophage content seen in 1.0 μm sections. The bands were present in rudimentary form at hatching. Lymphoid nodules began to develop at day 3 and were morphologically mature at day 98 posthatching. When viewed in the scanning electron microscope, the mucosa of the lymphoid areas was seen to be arranged in tortuous folds, often with irregular fusions. Following hormonal bursectomy, the bands were present, although difficult to detect, and lacked distinct nodules and germinal centres. The mucosal surface still appeared irregularly folded in the SEM, but the folds were more slender with convoluted surfaces.     

Pre-natal development of the adrenal gland in the mallard duck (Anas platyrhynchos)

Summary The differentiating nephrotome in the 10-day-old mallard duck embryo is able to synthesize corticosterone, aldosterone and deoxycorticosterone even though an adrenal anlage cannot be identified histologically until the 12th day of incubation. At this time, sudanophilic cells containing much smooth endoplasmic reticulum and numerous mitochondria with tubular cristae are located adjacent to the developing mesonephros. Chromaffm cells appear in this region on about the 14th day of embryogenesis. A discrete glandular structure containing measurable quantities of corticosteroids can be identified on the 15th day, and during the next 2 days the tissue becomes encapsulated. Concomitantly, the ACTH-inducible rates of corticosteroid hormone synthesis increase several fold. The corticotropic responsiveness of the developing adrenal steroidogenic tissue increases progressively during the remainder of embryogenesis.This work was supported by grants to James Cronshaw and W.N. Holmes from the University of California Committee on Research and the National Science Foundation (DIR-8820923), Washington, DC, USA     

Ultrastructure of the granulosa cells of the ovarian follicle of ducks (Barbary duck: Cairina moschata, Pekin duck: Anas platyrhynchos]

In the granulosa cells of the ovarian follicle of the ducks, the Golgi apparatus is developed, the granular endoplasmic reticulum is important. Owing to these characters, these cells are probably oriented towards the elaboration of proteins. The seasonal variations of the aspect of these cells are important: in January all organits are not very developed when in May they are all very developed. For a determined season all cells present the same aspect.     

Urocortin-like immunoreactivity in the primary lymphoid organs of the duck (Anas platyrhynchos)

Urocortin (UCN) is a 40 aminoacid peptide which belongs to corticotropin-releasing factor (CRF) family. This family of peptides stimulates the secretion of proopiomelanocortin (POMC)-derived peptides, adrenocorticotropic hormone (ACTH), β-endorphin and melanocyte-stimulating hormone (MSH) in the pituitary gland. In the present study, using Western blotting and immunohistochemistry, the distribution of UCN in the primary lymphoid organs of the duck was investigated at different ages. In the cloacal burse and thymus, Western blot demonstrated the presence of a peptide having a molecular weight compatible with that of the mammalian UCN. In the cloacal burse, immunoreactivity was located in the medullary epithelial cells and in the follicular associated and corticomedullary epithelium. In the thymus, immunoreactivity was located in single epithelial cells. Double labelling immunofluorescence studies showed that UCN immunoreactivity completely colocalised with cytokeratin immunoreactivity in both the thymus and cloacal burse. Statistically significant differences in the percentage of UCN immunoreactivity were observed between different age periods in the cloacal burse. The results suggest that, in birds, urocortin has an important role in regulating the function of the immune system.Key words: cloacal burse, thymus, cytokeratin, medullary reticular epithelial cells, CRFUrocortin (UCN) is a 40-amino acid peptide belonging to the mammalian corticotropin- releasing hormone (CRH) family which was first discovered in the rat midbrain (Vaughan et al., 1995). On the basis of its selective ability to bind CRH-receptor type 2 (CRH-R2), different types of UCN, i.e. UCN1, UCN2 and UCN3, have been identified (Lewis et al., 2001; Reyes et al., 2001). In mammals, UCN has been found in the central nervous (Vaughan et al., 1995), digestive (Muramatsu et al., 2000) and immune systems (Bamberger et al., 1998; Kageyama et al., 1999; Baigent et al., 2000), and in genital organs (Petraglia et al., 1996). UCN has also been found to play a role in regulating some CRH-receptor-mediated effects (Turnbull et al., 1999). While UCN2 and UCN3 selectively bind to CRH-R2, UCN1 binds to both CRH-R1 and CRH-R2 and shows a greater affinity to CRH-R2 than CRH alone (Chalmers et al., 1996). Despite the ability to interact with the same receptors, different functions are attributed to UCN and CRH. CRH is the primary neuroregulator of the vertebrate stress response in so far as it has been shown to be the major hypothalamic releasing factor for pituitary adrenocorticotropic hormone, whereas UCN seems not to be involved in the activation of the hypothalamus- hypophysis-adrenal axis (Turnbull et al., 1999). Conversely, UCN influences the function of the cardiovascular and nervous systems by increasing anxiety, decreasing appetite and influencing behavioral activity (Latchman, 2001). In non-mammalian vertebrates, few data have been reported on the presence and the role of UCN.The molecule, however, may have been conserved during vertebrate evolution, given that it has also been detected in amphibians and birds (Kozicz et al., 2002; Cavani et al., 2003; Boorse et al., 2005; Calle et al., 2005). In amphibians, UCN and CRH receptors have been found in the brain as well as in many other organs and tissues, including the pituitary gland, heart, kidney and alimentary canal (Kozicz et al., 2002; Boorse et al., 2005, 2006); thus suggesting a potential role for diverse actions in tissue maintenance and function. In Xenopus laevis, UCN injected in the third ventricle has been found to suppress food intake (Boorse et al. 2005). Moreover, it has been found to act as a cytoprotective factor in tadpole tail during metamorphosis (Boorse et al. 2006). In birds, UCN-ir has been found in neurons of the pigeon paramedian subgriseal mesencephalon which appear to be part of the brain circuitry involved in sympathetic nervous system-mediated behavioral responses to stress (Cavani et al. 2003; Cunha et al., 2007). Intracerebroventricular administered UCN, moreover, has been reported to decrease food intake in the chicken (Zhang et al., 2001). Up until now, however, no data are available regarding the presence and role of UCN in tissues and organs of birds outside the central nervous system (CNS). Since UCN and its receptors have been reported to be extensively expressed in immune tissues and addressed to play important roles in the regulation of the immune response (Baigent, 2001), the present study has investigated the presence and distribution of UCN in the primary lymphoid organs of the duck by means of Western blotting and immunohistochemistry. In addition, in order to verify if UCN also plays a role in the maturation of bird primary lymphoid organs, UCN expression was evaluated at different age periods.